Diacetylene Single Crystals

Markus Schwoerer, Elmar Dormaim, Thomas Vogtmaim, and Andreas Feldner 

122 Macromolecular Systems Microscopic Interactions and Macroscopic Properties Deutsche Forschungsgemeinschaft (DFG) 

Copyright 2000 WILEY-VCH Verlag GmbH, Weinheim. ISBN 978-3-527-27726-1 

The diacetylene with R = R = paratoluylsulfonyloximethylene is termed TS6 (sometimes TS). It was shown by G. Wegner and his co-workers in a series of works, pubhshed in the early 1970s [1, 7], that large molecular crystals can be grown from a solution of TS6, e.g. in acetone, and that these monomer diacetylene crystals can be converted by a topo-chemical (or solid state) 1,4-addition reaction to the polydiacetylene single crystals (Fig. 9.2). The crystal structures of TS before and after the reaction have been investigated in detail by Kobelt and Paulus [8], Bloor et al. [8], and Enkelmann [9] and are sketched in Fig. 9.3 and in Tab. 9.1. 

Both crystal structures are monoclinic with two monomers or monomer units of different orientation per unit cell (Fig. 9.3 sketches only one of these two.). The chemical bond between two carbons of nearest neighbour diacetylenes (1,4-addition) results in the linear polymer chain and the small change in the lattice parameter along the b-axis prevents the destruction of the macroscopic single crystal during the topochemical reaction. Several surfaces of diacetylene crystals have been studied by atomic force microscopy (AFM) in order to investigate both, the single crystal surface structure and solid state reactions at the surface [129, 131]. 

---

In addition to studies of diacetylene single crystals, current research, activities are focused on studies of the second X and third x order nonlinear optical responses of disubstituted diacetylene polymer films as active optical guided wave structures. Diacetylene polymers possess X values comparable to germanium(j 7). In the first stage, three major questions are being addressed ... 

Figure 6.1-23 Resonance CARS spectra of a substituted diacetylene single crystal (FBS-DA) at 10 K. The pump wavelength Xp used is labeled for each spectrum, (a) and (b) show CARS spectra of the P-colour zone, and (c)-(l) those for the Y-coiour zone. Spectra on the left side correspond to the C=C stretching region, and those on the right side to the C=C stretching region. For further details, see text (Materny and Kiefer, 1992b).

This contribution gives a review of recent spectroscopic investigations concerning the photophysical and photochemical primary and secondary processes of the solid state polymerization reaction in diacetylene single crystals. It will be shown, that diacetylenes are an unique model system for the study of the reaction mechanism of a solid state chemical reaction which is characterized by a variety of reaction intermediates. The polymerization reaction in these crystals is of special importance, due to the resulting polymer single crystals, which exhibit extraordinary anisotropic physical properties. 

Materny, A. Kiefer, W. Absorption, luminescence, resonance Raman, and resonance CARS spectroscopy on FBS diacetylene single crystals with color zones. Macromolecules 1992, 25, 5074-5080. 

The solid-state polymerisation of the diacetylenes can be initiated thermally and/or through irradiation with UV or y radiation and leads for many substituents R to macroscopic poly-diacetylene single crystals. For most substituents R, it is irreversible. Table 2.5 gives a selection of substituents R with which macroscopic diacetylene crystals have been successfully grown. Additional examples can be found in Enkelmann [11]. 

The poly diacetylene single crystals are fiber-like with high aspect ratio. 

Macro Crystals.—Nearly defect-free crystals of polymers have been produced by direct polymerization of monomer at gas-solid or liquid-solid interface. Poly-(diacetylene) single crystals have been produced from irradiation of the crystalline monomer and involves the instantaneous polymerization and crystallization of... 

The nearly defect free nature of diacetylene single crystals offers a unique opportunity for the study of the topochemical polymerization reaction. The goal of this paper is to summarize three years of study on some structural aspects of this polymerization process by X ray scattering techniques. We shall try to show what kind of information can be collected depending upon the price we are ready to pay for it. The results will concern two representative compounds,... 

MICROSTRUCTURES AND POLYMER CHAIN LENGTH IN DIACETYLENE SINGLE CRYSTALS... 

H. Niederwald, H. Seidel, W. Guttler, M. Schwoerer. Submicron Structures on Diacetylene Single-Crystal Surfaces by Electron Beam Irradiation. J. Phys. Chem. 88 (1984) 1933... 

M. Schwoerer, H. Niederwald, Photopolymerization of Diacetylene Single-Crystals. Makromol. Chem. (1985) (in press)... 

Under favourable packing conditions, diacetylene single crystals exposed to heat, radiation, or pressure react to form high quality polydiacetylene single crystals. Structural aspects of monomer reactivity are fairly well understood (at least at a qualitative level) via models based on least motion principles. However, there remain many unanswered questions regarding the detailed chemistry and physics of reaction initiation, propagation, and termination. 

Figure 9.6 Absorption spectra of a thin TS diacetylene single crystal for light polarized parallel and perpendicular to the polymer axis b (T = 300 K). Monomer (M) and polymer (P) absorption.

Since about 1980 and especially during our work for the Sonderforschungsbereich 213 we have synthesized several new diacetylenes, the substituents of which are shown in Tab. 9.2 [15]. For selected diacetylene single crystals we have investigated ... 

The present paper is a review of our work with diacetylene single crystals. 

We used diacetylene single crystal platelets, approx. 20 pm to 200 pm thick and some mm in area, cleaved from a parent TS6 crystal parallel to the (100) surface. 

---